Approved at the 26th meeting of the Nuclear Science Committee in June 2015 [NEA/SEN/NSC(2015)2]

Revised and extended at the 15th Meeting of the Working Party on Scientific Issues of the Fuel Cycle in February 2017 [NEA/SEN/NSC/WPFC(2017)2]

Mandate of the Expert Group on Liquid Metal Technology [NEA/SEN/NSC/WPFC(2018)1]

Mandate (Document extract):

Extract from document [NEA/SEN/NSC/WPFC(2018)1]

Introduction

The Expert Group on Heavy Liquid Metal (HLM) technology has been active for several years. Its main objective up to now was to issue a handbook with a collection of theoretical approaches and experimental data in order to deliver recommendations relevant for the design of HLM nuclear systems. Since the second version of the handbook is ready for publication, the EG has re-discussed its scope and future related activities. In particular, as suggested by the Working Party on Scientific Issues of the Fuel Cycle (WPFC), it has been decided to include liquid Na activities in the future work plan of the EG. Secondly, the EG will aim to take the next step in the assessment of available data to bring it closer to application in design, construction and licensing issues on the one hand and operation, In-Service Inspection, handling and maintenance on the other hand. After the discussion the EG proposes to formulate its objectives as follows.

Objectives & Scope

Under the guidance of the Working Party on Scientific Issues of the Fuel Cycle (WPFC), the expert group will undertake activities with the goal to "translate" fundamental scientific understanding to application in support of (1)Development of construction codes used for design (design rules), (2) Key technical issues for licensing, (3) Recommendations for Operation, Inspection and Handling.

The topical areas and objectives of the expert group are:

Environmental conditions and factors that affect materials behaviour relevant for the structural integrity of confinement barriers and components. These include the impact on mechanical properties from the environment such as irradiation effects and liquid metal embrittlement as well as environmental assisted property effects like corrosion.

The objective is to assess the environmental effects relevant for construction standards via a fundamental understanding of materials behaviour (corrosion and mechanical properties in the liquid metals and under irradiation). The possibility of experimental data sharing among participants and analyses is to be investigated.

Coolant and cover gas issues. The focus is placed on issues relevant for radiological impact assessment, operation, including maintenance, inspection and handling, etc. Topics to be addressed are the chemistry, radiochemistry and physics of the coolant, its interaction with the cover gas, the impact of irradiation, the influence of corrosion, transport of radionuclides in the coolant, etc.

The objective is to answer key technical issues to address radiological impact, operation, handling, maintenance and inspection as relevant for licensing.

Thermal-hydraulics for Liquid metals. Thermal hydraulic behaviour of the coolant is a crucial factor in the sense that it essentially determines a large part of the environmental conditions for materials and the cooling such as the flow distribution and mixing,temperatures distribution, stratification and instabilities, pressure variations, coolant structure interactions, etc.:

The objective is to collect and assess experimental data in order to improve knowledge of the environmental conditions for materials and the coolant behaviour.

Working Methods

Two taskforces (Na and HLM) will be established. To improve efficiency the taskforces will meet in parallel. At each meeting one plenary session will be organised to discuss and compare results in order to identify potential commonalities and synergies.

Activities

Survey current fundamental knowledge on the effect of liquid metal environment on material behaviour

Assess data management requirements with regards to the type of data, type of test and access conditions

Compile and assess data on the effect of liquid metal environment on material behaviour

The expert group will liaise closely with other NEA working groups, especially the Expert on Innovative Structural Materials and those operating under the guidance and the Committee on the Safety of Nuclear Installations (CSNI) in order to ensure the respective work programmes are complementary and to provide advice and support where required and undertake common work where appropriate.

The expert group will also work in co-operation with the IAEA Nuclear Power Technology Development Section and in particular the Technical Working Group on Fast Reactors (TWG-FR) and NAPRO (Sodium properties and safe operation of experimental facilities in support of the development and deployment of Sodium Cooled Fast Reactors). Key sources of experimental data to be reviewed include (but are not limited to) output from NAPRO, MatDB, etc.